One of the primary causes of vehicle engine failure is due to overheating. Cooling systems have been developed and designed over the years to maintain proper air flow across an engine's heat exchanger assembly(s). The three most common heat exchangers effected by the flow of cold air are the radiator, the A/C condenser and the charger air cooler (CAC). The CAC is located in front of the radiator and usually has between about a third and a fourth less surface area than the radiator. The CAC is a heat exchanger which cools the air exiting the turbocharger to a temperature optimal for re-introduction back into the engine through the intake manifold. Air leaving the turbocharger and entering the CAC is approximately 400.degree. F. Air exiting the CAC is approximately 150.degree. F. The CAC is an air-to-air heat exchanger; the fluid flow through the core and the fluid flow in the core are both the same. This is a low capacitance system which reacts quickly to temperature change.
Cooling systems are designed to operate with air flowing freely through the radiator and charge air cooler. However, during cold weather periods, cold air strikes the entire front surface of the grill of a moving vehicle and flows through the vehicle's heat exchanger assembly(s), thereby over-cooling these assemblies. Numerous attempts have been made in the prior art to prevent over-cooling of an engine's heat exchanger assemblies, the most of common of which is a device known as a winterfront. In general, a winterfront is a device which restricts the flow of cold air through the vehicle's heat exchanger assembly(s).
Winterfronts have found widespread use, particularly within the trucking industry. The most common type of winterfronts are designed to be mounted to the truck's grill, in order to block off a portion of the grill, thus decreasing the total amount of cold air impacting the cooling system and reducing the chance of over-cooling. For instance, U.S. Pat. No. 4,523,657 to Kooyumjian provides a winterfront composed of four polygonal sections of weather resistant fabric which are arranged over a truck's grill in such a manner to provide an adjustable central opening to restrict the flow of cold air impacting on the grill. Another example of a winterfront having a centralized opening is disclosed in U.S. Pat. No. 5,267,624 to Christensen. Christensen's winterfront comprises a centrally disposed, octagonal oval opening and an auxiliary X-shaped cover member which crosses the oval opening. U.S. Pat. Nos. 4,883,139 and Re 34,907 to Gross disclose a winterfront assembly which comprises a plurality of separate panel elements, each element being mounted within one of the grill's recesses.
Although winterfronts are effective in restricting the amount of cold air from striking the vehicle's heat exchanger assembly(s), there are serious drawbacks associated with the use of current winterfronts. Cooling systems require the free flow of air to run effectively. In fact, a recent study has suggested that an estimated 100,000 charge-air coolers will fail in 1998. The primary reason for this rate of failure is differential temperatures which cause thermal stresses in the CAC and radiator core. If a winterfront is arranged over a grill in such a manner that the air flow path is perpendicular to the path of the charge air flow, the cold air passing over the cooling tubes will decrease their expansion, while those tubes not receiving cool air through the winterfront will remain expanded. Thus, the covered areas will be hotter than the uncovered areas resulting in a differential stress. This discrepancy creates an inconsistent structural change to the tubes for which the charge air cooler cannot compensate and leads to fatigue failures. In addition to thermal stresses in the heat exchangers, fan stresses are developed in the fan blades by the loading and unloading of the airfoil as it passes the opening(s) disposed in the winterfront.
Current winterfronts concentrate the flow of cold air through one or more openings. Mechanical stresses are created by the distribution of flow across the frontal area of the cooling system component. If the openings are in proximal alignment to the center of the cooling component, the mechanical bending stresses are increased about the periphery. Truck manufacturers warn that improperly covering the grill in cold weather operation will interfere with the air flow which can result in under cooling. Under cooling can lead to excessive fan drive engagement and reduction of truck power due to fan rotation.
In addition to the above-described winterfronts, other types of assemblies have been developed for mounting to the grill of a vehicle. Curtain and shutter devices have been used as air-shielding or air-regulating assemblies for mounting to a vehicle grill. In U.S. Pat. No. 1,367,031 to Fedders a radiator curtain is described composed of a woven wire or similar fabric having three different sections of mesh such that the passage of air is obstructed. Other examples of curtains or shutters are disclosed in U.S. Pat. No. 1,818,328 to Hess, U.S. Pat. No. 2,198,123 to McCoy and U.S. Pat. No. 2,246,823 to Vollberg et al.
Another type of device which has been used in the prior art is the protective screen or filter to prevent insects, pollutants and other road debris from entering through a vehicle's grill and contaminating the engine and cooling system. An early example of such a screen is shown in U.S. Pat. No. 2,854,086 to Schmidt which discloses a conventional screen for preventing insects and dirt from passing through the grill and onto the engine. U.S. Pat. No. 3,815,700 to Mittendorf discloses a vehicle insect protection apparatus having a screen made of a plastic, fiberglass or metal material. U.S. Pat. No. 4,236,592 to Ziegler provides a structure for protecting the front surfaces of moving vehicles from insects and debris and modulating air flow through the vehicle radiator to control cooling efficiency. The Ziegler structure may be in the form of a cover of a screen material or of an impervious material for use during cold weather to limit and control air flow.
Despite the advances in the prior art, a need still exists for a winterfront which is capable of restricting the amount of cold air impacting a vehicle's heat exchanger assembly(s) but which provides a continuous and uniform flow of air across the entire frontal area of the cooling system. Such a winterfront should not compromise, but rather should maintain, the original flow configuration designed by the original equipment manufacturer, (OEM) which exposes the full frontal area of the cooling system to ambient and ram air conditions while at the same time should be capable of metering the impact of cold air in cold weather conditions. In addition, such a winterfront should provide a uniform air flow which decreases the mechanical and thermal stresses on the cooling systems components as well as reduce fan stresses.